A series of studies are being conducted to determine the following: 1) Whether the effects of stimulants, including dextroamphetamine and caffeine, on language production and speech fluency are similar in normal adults, normal boys, hyperactive boys and language impaired boys. 2) Whether auditory processing disorders occur in hyperactive boys who are without disorders in speech, language and reading. 3) Whether auditory processing skills in young adults are affected by the administration of dextroamphetamine. 4) Whether auditory processing disorders in hyperactive boys with and without disorders in speech, language and reading respond similarly to the administration of dextroamphetamine.